Auger type dredging heads are well known and usually comprise horizontal augers which are advanced along the bottom transverse to its path of movement similar to a reel-type lawn mower, see, for example, the patent to O'Brien U.S. Pat. No. 3,962,803 now assigned to the same assignee as the present invention. Such dredges have a pair of oppositely spiraled digging fins mounted on a common shaft and arranged that as the shaft is rotated the dredged material is moved by the spiraled fins towards the center where the inlet opening for a suction pipe is located.
It is also known to mount an auger type dredge head of the foregoing nature at the end of a dredge ladder but with the auger axis parallel to the axis of the ladder. With this arrangement the dredge operates with a side-to-side sweeping motion similar to a cutter head dredge. Such a dredge is shown in the patent to Norisugi U.S. Pat. No. 4,146,982.
A problem with both types of prior auger type dredges referred to above is that the dredge heads are designed to be mounted in one position only, either for linear movement as in the case of the O'Brien dredge or for sweeping movement as in the case of the Norisugi dredge.
Furthermore, because auger dredges usually operate adjacent the surface of a waterway bottom for the purpose of removing vegetation or other bottom material, heretofore strainer means have sometimes been provided in front of the auger to exclude solid bottom material, such as rocks, too massive to enter the inlet opening of a suction pipe from reaching the auger. The problem with a strainer is that it can be easily clogged causing frequent shut down to clear the strainer.